Migrates QUIC sessions to a new network when old network is (about to be) disconnected.

net/quic/quic_protocol.h

Index: net/quic/quic_protocol.h
diff --git a/net/quic/quic_protocol.h b/net/quic/quic_protocol.h
index a81660757aa1855cee61a9ed72cd1b4a4d255447..696144240dbe29b2fc149fb6df063fde2290f048 100644
--- a/net/quic/quic_protocol.h
+++ b/net/quic/quic_protocol.h
@@ -634,8 +634,20 @@ enum QuicErrorCode {
   // tampered with.
   QUIC_VERSION_NEGOTIATION_MISMATCH = 55,
 
+  // IP address changed causing connection close.
+  QUIC_IP_ADDRESS_CHANGED = 77,
+
+  // Connection migration errors.
+  // Network changed, but connection had no migratable streams.
+  QUIC_CONNECTION_MIGRATION_NO_MIGRATABLE_STREAMS = 78,
+  // Connection changed networks too many times.
+  QUIC_CONNECTION_MIGRATION_TOO_MANY_CHANGES = 79,
+  // Connection migration was attempted, but there was no new network to
+  // migrate to.
+  QUIC_CONNECTION_MIGRATION_NO_NEW_NETWORK = 80,
+
   // No error. Used as bound while iterating.
-  QUIC_LAST_ERROR = 77,
+  QUIC_LAST_ERROR = 81,
 };
 
 // Must be updated any time a QuicErrorCode is deprecated.